The effect of high K+ depolarization and verapamil on45Ca2+ fluxes in the canine myocardium
The effects of high K+ depolarization and verapamil on Ca2+ uptake and the total intracellular Ca2+ content of canine ventricular muscle strips (∼0.5 mm thick) were investigated. High K+ (96 mM) increased Ca2+ uptake above control and maintained this enhanced uptake throughout a 90 second measuring period. Verapamil (5×10−6M) significantly (p<0.05) inhibited this high K+ stimulated uptake. However, verapamil (5×10−6M) also had a direct effect on Ca2+ fluxes, causing a significant increase in both Ca2+ uptake (p<0.001) and total intracellular Ca2+ content (p<0.001) in the resting tissue. Therefore, verapamil's apparent inhibition of high K+ stimulated Ca2+ uptake may have resulted from some mechanism other than Ca2+ channel blockade.
Key wordsCanine ventricular muscle Calcium Potassium depolarization Verapamil
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